A wire grid polarizer (WGP) can transmit one polarization (e.g. p-polarization) and reflect or absorb an opposite polarization (e.g. s-polarization). High reflectivity of the opposite polarization (e.g. high Rs) can be important because some applications use both polarized light beams (e.g. s & p). High absorption/low reflectivity of the opposite polarization (e.g. low Rs) can be important in some applications because reflection of this polarization (Rs) can interfere with the optical system. For example, the reflected s-polarization can cause ghosting in an image projector. Some WGPs are designed for high reflection and others for high absorption of the s-polarization.
High transmission of one polarization (e.g. high Tp) can be an important feature of WGPs in order to minimize light-source power requirements. Low transmission of the opposite polarization (e.g. Ts) can be important for improved light image resolution. The quality or performance of WGPs can be shown by efficiency (Tp*Rs) and contrast (Tp/Ts).
Polarization can be improved by increased aspect ratio (wire thickness/wire width) of wires in a wire grid polarizer. Manufacture of wires with a sufficiently large aspect ratio is a difficult manufacturing challenge.